A Comparative Analysis of SET-LRP of MA in Solvents Mediating Different Degrees of Disproportionation of Cu(I)Br

Cu(I)Br/Me-6-TREN species are unstable and disproportionate into metallic Cu(0) and Cu(II)Br-2/Me-6-TREN in DMSO, whereas in toluene are stable and do not undergo disproportionation, at least at 25 degrees C. To estimate the role of the disproportionating solvent in single electron-transfer living radical polymerization (SET-LRP) a comparative analysis of Cu(0)/Me-6-TREN-catalyzed polymerization of MA initiated with methyl 2-bromopropionate at 25 degrees C was performed in DMSO and toluene. A combination of kinetic experiments and chain end analysis by 500-MHz H-1 NMR spectroscopy was used to demonstrate that disproportionation represents the crucial requirement for a successful SET-LRP of MA at 25 degrees C. In DMSO a perfect SET-LRP occurs and yields close to 100% conversion in 45 min. A first order polymerization in growing species up to 100% conversion and a PMA with perfectly functional chain ends are obtained. However, in toluene within 17 h only about 60% conversion is obtained, the polymerization does not show first order in growing species and therefore is not a living polymerization. Moreover, at 60% conversion the resulting PMA has only 80% active chain ends. (c) 2008 Wiley Periodicals, Inc.